1. Field of the Invention
The invention relates to a clamping device for workpieces that have been specially prepared for clamping in the clamping device, and a clamping method for workpieces.
2. Description of Prior Art
For machining in tool machines, the workpieces must be fixedly clamped and held at suitable clamping regions. The clamping setup must be designed such that, especially in machining processes in which material is removed from the workpieces, larger forces can also be readily diverted and therefore not cause a displacement of the workpiece. On the other hand, the workpiece should be as accessible as possible so that a wide range of machining processes can be performed on the workpiece in a single clamping setup. These two requirements are contradictory to some extent. If the workpiece is supposed to be accessible from, for example, five sides, a clamping that does not block access to the sides to be machined is required.
If workpieces are clamped between clamping jaws of a machine vise, for example, the two clamping jaws of the machine vise cover large areas of two oppositely-located sides of the workpiece. This impedes access to the workpiece.
In view of the above remarks, it is the object of the invention to provide a clamping device for workpieces, with which workpieces can be held securely, and which permits good access to the clamped workpieces.
This object is accomplished with the clamping device according to the present invention.
The clamping device has two clamping jaws or clamping elements, which are provided with form-fit elements whose embodiment is complementary to corresponding coupling elements of the workpiece. The coupling elements are embodied on the workpiece in a preparatory work step. They usually perform no other function than to serve in clamping the relevant workpiece in the clamping device of the invention. The form-fit elements of this device permit the workpiece to be fixed in, for example, an extremely narrow, strip-shaped region. The workpiece clamped in a frictional connection between the clamping elements is held by the form-fit elements and the coupling elements in an additional form-fit. It is therefore possible to clamp workpieces that project relatively far out of the space defined between the two clamping elements. Hence, machining processes that involve material removal, or other machining processes that exert considerable forces on both the side surfaces and the end face of the workpiece, can be performed on the workpiece, with the only limitation being the inherent elasticity of the workpiece. The workpiece is seated with only one very short base region between the two clamping elements, with the form-fit elements preventing the workpiece from being tipped out of the clamping jaws under the exertion of large forces. The form-fit elements are embodied to prevent or block any movement of the workpiece in any direction oriented parallel to the contact surfaces of the clamping elements. The provision of both clamping elements with corresponding form-fit elements prevents any rotational, pivoting or tipping movement of the workpiece. The form-fit elements transmit the corresponding retaining forces to the clamping elements, and divert them, regardless of whether the two clamping elements can be adjusted toward and away from one another, or only one of the two clamping elements is mobile. If the clamping elements are pressed against the workpiece so as to clamp it between themselves, the form-fit elements automatically engage the coupling elements and stop the workpiece.
In addition to the combination form-fit and frictional-lockup clamping or holding of the workpiece in the clamping device, the form-fit offers the advantage that the workpiece assumes a defined position relative to the clamping device from the outset. Erroneous positioning can be virtually precluded. Consequently, setting up the workpieces may require far less effort.
The form-fit elements, which can be embodied, for example, as projections or depressions on or in the clamping elements, are preferably integral to the clamping elements. This assures a high load-bearing capacity. Accordingly, the coupling elements of the workpiece are depressions or projections that are imprinted into or mounted onto the workpiece in a machining step prior to the clamping process. For example, the work step can be a stamping machining process in which the clamping region of the workpiece is slightly plastically deformed. This deformation is preferably effected in a region of the workpiece that is not impeded in function by the stamping of depressions or the mounting of projections. Particularly in workpieces in which such regions are absent, the coupling elements can also be discarded following the machining process. This is possible in, for example, a grinding or milling machining process that is performed in a different, possibly conventional, clamping setup.
The form-fit elements and coupling elements can be embodied in the manner of a toothing, for example. The individual teeth and the associated depressions are respectively equidistantly spaced. To assure a fixed clamping position, however, it is also possible to modify the distribution at a predetermined location, or omit an individual tooth or an individual depression.
The truncated-pyramid shape has proven advantageous for the form-fit elements and coupling elements. The frustoconical shape is also possible. In both cases, the form-fit elements engage the associated coupling elements relatively easily, especially if the flank angle of the form-fit elements is not too large. For example, it has proven advantageous for the angle formed by the side surfaces of the truncated-pyramidal projections and the contact surface to be no larger than 45xc2x0. The associated depressions serving as coupling elements can be stamped easily; while they are not very deep, they assure a good form-fit coupling between the workpiece and the clamping jaws.
The form-fit elements are disposed, for example, in a single, straight row on one edge of the clamping jaw. This permits a particularly compact, space-saving clamping of workpieces. Other arrangements are, however, likewise conceivable and plausible. If very large forces are to be absorbed, patterns consisting of, for example, two or more rows can be used.
If the form-fit elements and the coupling elements are identical in size, or even have some play relative to one another, a true separation of function between the contact surface and the form-fit element is effected: The contact surfaces serve in the frictional-lockup clamping, while the form-fit elements assume the function of fixing and securing the position of the workpieces during machining. The advantage of this embodiment is that the form-fit and coupling elements are not subjected to stress during the clamping; no stressing occurs until the machining process. If, however, the desired clamping is to permit effective suppression of even slight movements of the workpiece, it can be advantageous for the elements embodied as projections to be at least slightly larger than the associated elements embodied as depressions. The form-fit elements on the clamping elements are preferably dimensioned to be larger or smaller than specified, and the material of the clamping elements is preferably selected to limit the occurrence of plastic deformations of the workpiece, if they occur at all. Such clamping elements permit a long-term precise, reliable clamping of workpieces.